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Comments on the identification of Ammonites planula Hehl in Zieten, 1830 (Upper Jurassic, SW Germany)

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Schweigert G. , Kuschel H.

tom Vol. 15, no 1

1--16

Ammonites planula Hehl in Zieten, 1830 is the type species of the Late Jurassic ammonite genus Subnebrodites Spath, 1925 and the index species of the well-established Planula Zone of the Submediterranean Province. Recently, Enay and Howarth (2017) classified this stratigraphically important ammonite species as a ʻnomen dubiumʼ and considered it to be the possible macroconch counterpart of Idoceras balderum (Oppel, 1863). These authors claimed “Subnebrodites planula Spath, 1925” instead of Ammonites planula (Hehl in Zieten, 1830) to be the type species of Subnebrodites. However, their nomenclatorial acts are based on erroneous assumptions. For future taxonomic stability we here propose a neotype for Ammonites planula (Hehl in Zieten, 1830) and a lectotype for Ammonites planula gigas Quenstedt, 1888. In addition, dimorphism within the stratigraphically much younger Idoceras balderum (Oppel) is demonstrated showing that there is no morphological resemblance and no closer relationship with Ammonites planula (Hehl in Zieten, 1830).

Additional Tithonian and Berriasian ammonites from the Vaca Muerta Formation in Pampa Tril, Neuquén Basin, Argentina

80%

Parent H. , Schweigert G. , Scherzinger A. , Garrido A. C.

tom Vol. 15, no 1

139--154

The ammonite fauna of the Tithonian–Berriasian of the Vaca Muerta Formation in Pampa Tril has been recently described in detail. New important specimens and additional information are presented in this paper. The phyletic evolution of Choicensisphinctes, passing from C. platyconus to C. erinoides is confirmed, as well as the sexual dimorphic correspondence of this latter with C. mendozanus. A microconch of the genus Krantziceras is described for the first time. New specimens of Substeueroceras koeneni identical to the paralec¬totype, along with material already described from the koeneni Hz. (Koeneni Zone), point to the fixation of this horizon as the type horizon of the species. New specimens of Subthurmannia boissieri from the Damesi Zone match clearly the range of variation of this species in Spain, thus providing an element for time-correlation with the Tethyan standard scale. Additional material from the internispinosum alpha Hz. confirms the origin of W. internispinosum from C. proximus by the inception of an evolutionary innovation in the juvenile ontogeny.